This set of Biochemistry Multiple Choice Questions & Answers (MCQs) focuses on “G Protein – Coupled Receptors and Second Messengers”.
1. Which out of the following statements is true about G-protein couple receptors?
a) The N-terminal chain is extracellular and C-terminal chain is intracellular
b) It contains 5 trans-membrane hydrophobic sections
c) There are more extracellular loops than intracellular loops
d) The binding region for G-protein involves 2 extracellular loops
Explanation: GPCR is characterized by an extracellular N-terminus and an intracellular C-terminus.
2. Which of the following is not a G-protein coupled receptor?
a) Glycine receptor
b) Adrenergic receptor
c) Glutamate receptor
d) Muscarinic receptor
Explanation: Glycine receptor is a neurotransmitter but not a GPCR.
3. Protein kinase A is
a) Completely inhibited by cyclic AMP
b) Allosterically activated by cyclic AMP
c) Affected by cyclic AMP only under unusual circumstances
d) Activated by covalent binding of cyclic AMP
Explanation: Protein kinase A is activated when cAMP allosterically binds to a regulatory peptide.
4. Which out of the following is not involved in signal transduction by β-adrenergic receptor pathway?
Explanation: cAMP is not involved in signal transduction by β-adrenergic receptor pathway.
5. Which of the following catalyzes the cutting of PIP2 into 2 moles of IP3 and diacylglycerol in cell signaling?
a) Phosphokinase C
b) Phospholipase C
d) Phosphodiesterase C
Explanation: PLC also named as phospholipase grabs onto PIP2 and cuts it into diacylglycerol and IP3.
6. The binding of ligands to many GPCRs leads to
a) Decrease in concentration of certain intracellular signal molecules called second messengers
b) Increase in concentration of certain intracellular signal molecules called second messengers
c) Decrease in concentration of certain extracellular signal molecules called first messengers
d) Increase in concentration of certain extracellular signal molecules called first messengers
Explanation: The binding of ligands to many GPCRs leads to decrease in concentration of second messengers.
7. A hormone or ligand can be considered as
a) First messenger
b) Second messenger
c) Third messenger
d) Fourth messenger
Explanation: Hormones are often considered to be first messengers, IP3, cAMP and cGMP are considered to be second messengers.
8. Which of the following serves as a neurotransmitter in adrenergic neurons?
Explanation: Adrenaline or epinephrine serves as a neurotransmitter in adrenergic neurons.
9. Which second messenger signals the release of Ca+2 from endoplasmic reticulum?
b) 1,2 diacyl glycerol
Explanation: IP3 binds to the receptor present on endoplasmic reticulum causing it to release calcium ions.
10. GPCR is comprised of
a) 7 transmembrane helices
b) 8 transmembrane helices
c) 9 transmembrane helices
d) 10 transmembrane helices
Explanation: GPCRs are 7 transmembrane domain receptors.
Sanfoundry Global Education & Learning Series – Biochemistry.
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